Fictional planets from the Star Trek mythos Romulus and Remus are "twin worlds"- meaning they revolve around a point between themselves while revolving around a star. Romulus apparently had no sapient species until a proto-vulcan splinter group colonized it. These proto-vulcans overtime became the Romulans. A native sapient species developed on Remus and was conquered by the Romulans later becoming an lower class in Romulan society. A Reman coup briefly overthrew the Romulan senate and took control of the empire in Star Trek Nemesis.

In the Star Fleet Universe, the worlds are in neighbouring star systems, and both are populated by Romulans (as opposed to a separate Reman species). While both worlds are considered the capital worlds, Romulus has the larger economic value and houses the fleet shipyards.